Preconception and gestational versus postnatal exposure to air pollutants and risk of autism spectrum disorder: a systematic review and meta-analysis.

PURPOSE: The rising prevalence of ASD has prompted extensive research into potential environmental risk factors, with air pollution particularly emerging as a major concern. A systematic review and meta-analysis on the effect of air pollutants and time of exposure (particularly, PM2.5, PM10, NO2, and O3) and the risk of ASD was therefore performed.

METHODS

Following PRISMA guidelines and PROSPERO registration (Ref: CRD42023464592), a thorough literature search was conducted across multiple databases, including Scopus, PubMed/MEDLINE, Embase, PsycINFO, Web of Science, and Cochrane Library. The analysis included 27 studies encompassing 369,460 participants, 47,973 of whom were diagnosed with ASD.

RESULTS

Preconception exposure to air pollutants showed a protective trend for PM2.5, PM10, and O3 with a 10%, 5%, and 19% reduced risk of ASD, whereas NO2 had a 28% higher likelihood of ASD. During gestation, PM2.5 exposure increased ASD risk by 15%, with 13% and 9%, 25% and 7%, and 25% and 10% increases in ASD risk with PM2.5 and NO2 for the first, second, and third trimesters, respectively. In the first year of life, 20%, 8%, 33%, and 14% increases in risk were found for PM2.5, PM10, NO2, and O3, respectively, while such risk estimates increased to 179%, 60%, 12%, and 179% for the second year of life.

CONCLUSIONS

In this meta-analysis, the relationships between air pollutants and ASD risk revealed significant associations, particularly for PM2.5 and NO2. Exposure during preconception exhibited a protective trend, while postnatal exposure, particularly during the second year of life uncovered substantially higher ASD risk.